CN107869331A - Aleuritic texture ocean gas hydrate gravel is handled up recovery method and quarrying apparatus - Google Patents

Abstract

The invention discloses a silty marine natural gas hydrate gravel huff and puff mining method and a mining device. The mining method properly relaxes the sand-retaining accuracy of the wellbore, so that the formation fine sand and mud components flow into the wellbore. After a certain production time, the coarse Gravels of particle size are injected into the formation outside the production well pipe to fill the gap caused by formation fine components and hydrate output, and then the well is opened for production. In this way, the sand and gravel injection rounds and the hydrate reservoir fluid pumping rounds are alternately reciprocated to achieve It can improve the productivity of silty reservoirs, prevent large-area deficits in formations, and prolong the effective period of wellbore sand control. Gravel injection and depressurization production are carried out alternately, combined with appropriate sand production management technology, to realize intermittent huff and puff replacement of coarse-grained gravel and formation mud, sandy fine particles and hydrate decomposition space, and promote silty natural gas hydrate The high-efficiency depressurization of reservoirs can reduce the risk of formation instability and collapse during the long-term exploitation of marine natural gas hydrates, provide new ideas for the exploitation of silty hydrates in my country's sea areas, and promote the development of hydrate commercial exploitation technologies.

Description

Silty marine natural gas hydrate gravel huff and puff mining method and mining device

technical field

The invention belongs to the field of high-efficiency exploitation of marine natural gas hydrate, and in particular relates to a silty marine natural gas hydrate gravel huff and puff mining device and mining method.

Background technique

Gas hydrate is widely distributed in high-latitude terrestrial permafrost and continental margin sea sediments. It is an important potential energy source. How to exploit and utilize it safely and efficiently has become a current international research hotspot. In recent years, the research focus of various countries in the world has gradually shifted from the original hydrate basic research and hydrate resource exploration to the stage of gas hydrate trial production. In particular, countries with relatively short conventional oil and gas resources, such as Japan, have carried out a large number of researches on the trial production of natural gas hydrate in sea areas and formulated medium and long-term industrialization goals for hydrate production. From the perspective of mining methods, the current natural gas hydrate mining methods are mainly divided into depressurization mining method, heat injection mining method, CO ₂ displacement mining method and chemical agent injection mining method in terms of mechanism. From the trial mining to the trial mining of water in the South China Sea in 2017, some or all of the above mining methods have been verified by field tests.

All previous test production practices have shown that the depressurization production method is the most promising natural gas hydrate production method. However, whether it is the first trial production of natural gas hydrate in sea areas in my country or the previous trial production of hydrates abroad, they are all in the stage of scientific experiments, and there are still many key technologies to be solved before industrialization. The depressurization method still faces key problems such as formation instability and large-scale sand production in the process of mining natural gas hydrate in sea areas, which makes it difficult to increase production in long-term mining. Especially for the silty hydrate reservoirs distributed in a large area in my country's sea area, the improved fluid extraction method based on the conventional depressurization method has achieved success in short-term test production (60 days). However, due to the small particle size and high clay content of this type of reservoir sediment, it is an extremely weakly consolidated low-permeability or ultra-low-permeability reservoir. It will have a serious impact on the productivity of production wells; on the contrary, if the sand-retaining accuracy of the wellbore is slightly enlarged, the fine particles or muddy particles in the formation near the wellbore will easily flow into the wellbore, and over time, it will inevitably lead to a deficit in the formation near the wellbore. Due to the superimposition of the deficiency caused by the production of fine formation components and the deficiency caused by hydrate decomposition, the reservoir will face serious stability problems. , need to further improve and optimize the depressurization method—in depressurization mining, other substances need to be injected into the reservoir to solve the above problems.

The CO ₂ replacement production method provides an idea for maintaining the stability of gas hydrate reservoirs, but because this method will form CO ₂ hydrate during the replacement process, which will reduce the permeability of the formation near the wellbore, making continuous production difficult in the later stage. This method still faces serious production efficiency problems in large-grained sandy reservoirs (IgnikSikumi-2012 trial production in the United States), but its application effect can be imagined for silty reservoirs. Therefore, although the _CO2 replacement method can provide some reference ideas for long-term hydrate mining, the practice of replacing hydrates with hydrates is obviously not available in the long-term mining of silty hydrates. If we can find a way to replace hydrates with other high-permeability substances (while replacing near-well mud or fine silt), it will have a revolutionary impact on the long-term production of hydrates.

If the above-mentioned _CO2 is replaced by hot steam injection, the _CO2 replacement method is the heat injection method in the usual sense. Although this method helps to maintain formation pressure and slow down formation instability to a certain extent, it cannot fundamentally solve the problem of formation instability, and it has been proved by Mallik 2L-38 hydrate test production that it is effective for marine gas hydrates. Mining applicability is very limited. In the development of conventional heavy oil reservoirs, steam huff and puff is often used to achieve single well production increase. At present, it has been very maturely applied. However, for marine gas hydrate reservoirs, the efficiency of steam huff and puff and the impact on reservoir stability The degree of improvement is not optimistic. Therefore, in terms of actual demand, hydrate mining needs to be "suffering and puffing", but the substance "suffering and puffing" must not be steam, but a substance that can not only promote the decomposition of hydrates, but also fill the void in the formation.

In 2013, Japan's first offshore natural gas hydrate trial production project adopted the sand control technology of gravel packing outside the open hole pipe, and achieved the effect of 120,000 cubic meters of natural gas in 6 days, which greatly encouraged the confidence of global marine natural gas hydrate research. The gravel layer outside the pipe played a very good dual role of increasing productivity and sand control in the early stage of production, but with the termination of the test production, the "open hole gravel packing outside the pipe" sand control completion process was deemed unsuitable for offshore gas hydrate production The "wrong hat" of the well: Because during the process of hydrate decomposition, the formation space outside the pipe gradually becomes larger, and the gravel packing layer creeps and becomes void, causing the produced fluid to directly impact the screen, causing erosion damage soon, resulting in a sharp increase in the effective period of sand control. decline (6d), the hydrate trial mining was forced to terminate.

To sum up, there are still the following key issues to be resolved between the current natural gas hydrate exploitation method and the actual demand on site:

1. The depressurization method cannot solve the formation deficit problem under long-term hydrate mining conditions, and conventional sand control operations are faced with the challenge of sand control failure caused by formation deficit;

2. The long-term stable hydrate production urgently needs to fill or replace the formation deficit in time, but the CO ₂ replacement method can only solve the deficit caused by the hydrate output but cannot solve the deficit caused by the formation mud sand output, and also impact on the further production of gas hydrates;

3. The steam huff and puff method has been widely used in the exploitation of conventional heavy oil reservoirs, but the "steam" huffed and puffed by the steam huff and puff method can only promote the decomposition of hydrates and cannot fill the formation deficit;

4. Although the one-time openhole gravel packing sand control completion operation can play a good role in the short term, the sand control period is short due to the lack of follow-up source supply, which is not enough to meet the long-term demand for offshore natural gas hydrate exploitation.

Therefore, it is urgent to propose a new type of development method that can prevent large-area deficits in the formation. Combined with the commonly used depressurization method, it can fundamentally solve the severe sand production and formation failure encountered in the current sea area natural gas hydrate test production process. Stabilizing engineering geological disasters is crucial to prolonging the life cycle of natural gas hydrate exploitation, and it is also helpful to effectively promote the industrialization of natural gas hydrate in my country's sea areas.

Contents of the invention

The technical problem to be solved by the present invention lies in the contradiction between increasing production capacity, sand control measures and stratum instability in the process of depressurization or fluid extraction in the large-area distribution of clayey silt in my country, based on Based on the concept of sand production management, a silty marine natural gas hydrate gravel huff and puff mining device and mining method are proposed.

The present invention is realized by adopting the following technical scheme: a method for huffing and puffing mining of silty marine natural gas hydrate gravel, comprising the following steps:

(1) Drill to the target layer, and complete the hydrate reservoir with open-hole screens;

(2) Install and run the wellbore string assembly;

(3) Carry out circular gravel packing outside the screen, observe the change of packing pressure, and stop packing in time;

(4) Without removing the original string combination, adjust the valve process, open the well for production, and observe the formation sand production and the change of bottom-hole production pressure difference in real time;

Steps (3) and (4) are timely switched and alternately performed according to the time node, so that the injected gravel can continuously fill and replace the formation deficit, and maintain the long-term production of marine silty gas hydrate.

Further, the step (1) is realized by the following methods: opening the hydrate reservoir, using the production casing to seal the overlying formation of the hydrate reservoir, lowering the mechanical screen pipe, and performing independent screening of the hydrate reservoir under the open hole The well is completed with pipes, and the bottom of the artificial well is drilled; the installation interface of gravel packing tools is reserved between the mechanical screen and its upper production casing.

Further, in the step (2), the installation method of the string combination is as follows: the gravel packing tool, the production tubing and the packing string are lowered, the production tubing and the packing string are located in the production casing, and the packing string is connected to the production casing respectively. The oil pipe is connected with the gravel packing tool. The gravel packing tool is located at the top boundary of the hydrate reservoir, and a control valve and a gas separator are installed at the inlet end of the production oil pipe. valve, and the gravel packing tool is also provided with a filling switching valve.

Further, during the gravel packing process in step (3), close the one-way control valve on the lower side of the gravel packing tool, open the gravel packing conversion valve, close the control valve at the lower end of the production tubing, and flow through the channel formed by the packing string and the gravel packing tool to the Sand and gravel are injected outside the mechanical screen to form a sand and gravel packing layer. During the injection of sand and gravel, the sand-carrying liquid passes through the mechanical screen and returns to the platform wellhead from the wellbore annulus. The wellbore annulus is the outer wall of the production tubing and the packing string and the production casing. The annular space formed by the inner wall of the pipe; observe the pressure change of the outlet of the mortar injection pump during the gravel injection process, when the gravel injection pressure gradually increases from P ₀ to P ₁ , stop the gravel injection, and transfer to the next production stage, the P ₀ is the starting pressure of gravel injection, and P ₁ is the maximum pressure of gravel injection.

Further, during the transition from step (3) to step (4): open the one-way control valve on the lower side of the gravel packing tool, close the gravel packing switching valve, open the control valve at the lower end of the production tubing, and start the lift pump to pump the formation fluid , start step-down production;

The gas-liquid-solid three-phase produced from the hydrate reservoir in the process of step (4) flows into the wellbore and is separated by the gas separator. The liquid-solid two-phase flows to the wellhead through the production tubing, and the gas is produced through the annulus of the wellbore ;

During the implementation of step (4), real-time monitoring of sand concentration parameters at the wellhead and changes in bottomhole flow pressure, if there is a sudden increase in sand concentration or a sudden increase in bottomhole flow pressure difference, stop further depressurization production and turn to Enter step (3).

Further, in the process of step (4), it also includes the process of continuously injecting water or liquid containing hydrate inhibitors into the production tubing from the filling string, so as to ensure that all the fine sand produced in the formation can be carried to the wellhead while preventing hydrate secondary generation.

Further, the time node from step (4) hydrate depressurization production process to step (3) gravel injection is judged according to the abnormal sand production in the wellbore, or the sudden change in the production pressure difference at the bottom of the well without artificial pressure adjustment; Step (3) Gravel injection transfer to step (4) Hydrate depressurization production time point is that the gravel injection pressure rises rapidly and cannot continue to inject; Among them, the basis for judging abnormal sand production in the wellbore includes bottom hole pressure fluctuations, lift The phenomenon of pump sand mill heating up and wellhead monitoring sand concentration increasing appears.

Further, the particle size of the gravel used for filling in the step (3) is larger than that of grade 1-2 in the design result of the Saucier method under the same mining environment.

Further, the particle size of the sand and gravel used for filling in the step (3) is larger than the grade 1 to grade 2 design results using the Saucier method under the same formation conditions; the sand retaining precision of the mechanical screen in the step (1) is greater than that in the same formation The precision of the mechanical screens used in open hole gravel packing of conventional oil and gas wells under these conditions is grade 2-3.

In addition, the present invention also proposes a silty marine natural gas hydrate gravel huff and puff production device, which includes a production casing, a production tubing and a filling string arranged in the production casing, and a lifting string is also arranged in the production tubing. The tubing string is connected to the lift pump, and the gap formed between the outer wall of the production tubing and the filling tubing string and the inner wall of the production casing is the wellbore annulus;

The lower end of the production casing is connected with a mechanical screen, and a gravel packing tool is also arranged between the production casing and the mechanical screen. The production casing is lowered to the position above the hydrate reservoir, and the gravel packing tool is located at The top boundary of the hydrate reservoir, and the mechanical screen is located in the hydrate reservoir section below it. The gravel packing tool can depressurize the wellbore without being pulled out. In addition, a gas separation device is installed at the lower end of the production tubing. devices and control valves;

The outlet end of the packing string is respectively connected with the gravel packing tool and the production tubing, a one-way control valve is set at the connection between the gravel packing tool and the production tubing, and a packing switching valve is also set on the gravel packing tool, and the packing string is The lower part of the gravel packing tool is connected to the production tubing. When the gravel is injected, the packing string will fill the formation outside the production casing with sand-mixed mortar separately. During the production stage, water can be added to the production tubing to carry sand in the wellbore.

Compared with prior art, advantage and positive effect of the present invention are:

(1) The scheme of the present invention replaces the solid phase (mud, sandy fine particles and hydrate) through solid phase (large-diameter gravel) huffing and puffing, and adopts operations such as appropriately relaxing the sand-retaining precision of the mechanical screen and selecting suitable filling gravel. , to help discharge the mud or fine particles in the formation near the wellbore in time during the hydrate decomposition process, prevent the wellbore from clogging, and effectively overcome the high mud content, low permeability, and unsuitable fracturing of the marine silty hydrate reservoir, etc. Insufficient, and effectively improve the pressure transfer efficiency of the wellbore and near-wellbore formations, escorting the hydrate depressurization/fluid extraction production wells to increase production;

(2) Intermittently stop depressurization/fluid pumping production and squeeze sand and gravel into the formation outside the pipe to replenish the formation deficit in time, effectively prolong the effective period of sand control and depressurization production cycle, and effectively solve the problems caused by long-term hydrate production. Formation deficit and formation instability, prolonging the depressurization/fluid pumping production cycle, and providing a basis for the industrialized production of hydrates;

(3) This scheme is suitable for marine gas hydrate reservoirs with high shale and silty sand that are not suitable for complete sand control and reservoir reconstruction, and is suitable for pore-filling reservoirs or natural gas hydration with thin block hydrate interlayers. It solves the problems of low efficiency of CO ₂ displacement mining of marine natural gas hydrate, difficulty in maintaining reservoir stability in heat injection mining, and short validity period of sand control operation of gravel filling outside the pipe in advance, and solves the problem of natural gas hydrate mining production capacity in China's sea areas. Improve the difficulty and high risk of reservoir instability, and promote the development of hydrate commercial mining technology.

Description of drawings

Fig. 1 is a schematic diagram of gravel injection in a gravel huff and puff mining device in an embodiment of the present invention;

Fig. 2 is a schematic diagram of the outflow of formation output from the gravel huff and puff mining device in the embodiment of the present invention;

Fig. 3 is a schematic diagram of the progress of the gravel huff and puff mining cycle in the embodiment of the present invention;

Among them, 1—production casing; 2—production tubing; 3—packing string; 4—gravel packing tool; 5—one-way control valve; 6—mechanical screen; 7—gravel packing layer; 8—hydrate reservoir ;9—overlying formation of hydrate reservoir; 10—gas separator; 11—control valve; 12—gravel packing switching valve; 13—wellbore annulus; P ₀ —starting pressure of gravel injection; P ₁ —maximum pressure of gravel injection .

Detailed ways

In order to understand the above-mentioned purpose, features and advantages of the present invention more clearly, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

The invention proposes a new idea of huff and puff mining of silty marine natural gas hydrate gravel. By injecting gravel with a certain particle size into the exploited stratum, the stratum can "swallow" the gravel, and continuously fill the hydrate decomposed and stratum mud. Formation shortage space caused by the formation; application of offshore natural gas hydrate sand production management technology, appropriately relax the fracture width of the mechanical screen and the particle size of the swallowed gravel, so that the mud and fine particles in the formation near the wellbore can be discharged from the formation in a certain proportion , to realize the "vomiting" of formation fine components. Through the above material exchange, the huff and puff replacement of formation fine components and coarse-grained gravel can be realized, which can effectively fill the formation deficit and prevent formation instability while improving near-well permeability and promoting hydrate formation. Effective decomposition provides new ideas for the mining of silty hydrates in China's sea areas, specifically through the following schemes:

Embodiment 1, a method for huffing and puffing mining of silty marine natural gas hydrate gravel, referring to the structural principle described in Fig. 1 and Fig. 2, includes the following steps:

(1) Drill to the target layer, and complete the hydrate reservoir with open-hole screens;

(2) Install and run the wellbore string assembly;

(3) Carry out circular gravel packing outside the screen, observe the change of packing pressure, and stop packing in time;

(4) Without removing the original string combination, adjust the valve process, open the well for production, and observe the formation sand production and the change of bottom-hole production pressure difference in real time;

Steps (3) and (4) are timely switched and alternately performed according to the time node, so that the injected gravel can continuously fill and replace the formation deficit, and maintain the long-term production of marine silty gas hydrate.

Specifically, in step (1), the gas hydrate reservoir 8 is opened according to conventional drilling operation measures in shallow oceanic formations, the production casing 1 is used to seal the overlying strata 9 of the hydrate reservoir, and the mechanical screen 6 is lowered. The hydrate reservoir 8 is completed with an independent screen in the open hole, and an artificial well bottom is drilled; the installation interface of the gravel packing tool 4 is reserved between the mechanical screen 6 and the upper production casing 1 . In step (2), the installation method of the string combination is to lower the gravel pack tool 4, the production tubing string 2 and the packing string 3, the production tubing 2 and the packing string 3 are located in the production casing 1, and the packing string 3 is respectively It communicates with the production tubing 2 and the gravel-packing tool 4. The gravel-packing tool 4 is located at the top boundary of the hydrate reservoir 8, and a control valve 11 and a gas separator 10 are installed at the inlet of the production tubing 2. The gravel-packing tool 4 and the production A one-way control valve 5 is also provided at the connection of the oil pipe 2 , and a gravel packing switching valve 12 is also provided on the gravel packing tool 4 .

Step (3) During the gravel packing process, close the one-way control valve 5 on the lower side of the gravel packing tool 4, open the gravel packing switching valve 12, close the control valve 11 at the lower end of the production tubing 2, and use the gravel packing tool 4 left at the bottom of the well to , through the channel formed by the packing string 3 and the gravel packing tool 4, sand and gravel are injected to the outside of the mechanical screen 6 to form a sand and gravel packing layer 7. During the injection of sand and gravel, the sand-carrying liquid passes through the mechanical screen 6 and returns from the annulus 13 of the wellbore. To the wellhead of the platform, the wellbore annulus is the annulus formed by the production tubing and the outer wall of the packing string and the inner wall of the production casing; observe the injection pressure changes during the gravel injection process, as shown in Figure 3. When the gravel injection pressure is gradually increased from P ₀ to P ₁ , the gravel injection is stopped, that is, when the pressure is observed to increase significantly, it is transferred to the next production stage. The P ₀ is the starting pressure of the gravel injection, and P ₁ is the maximum Pressure, the maximum pressure _P1 of gravel injection is determined according to the formation fracture pressure gradient. In order to ensure that no formation cracks or pressure through the seabed mud surface are generated during huff and puff production, it is necessary to ensure that _P1 is less than or equal to the formation fracture pressure or the pressure of the overlying seabed mud surface.

During the transition from step (3) to step (4), open the one-way control valve 5 on the lower side of the gravel packing tool 4, close the gravel packing switching valve 12, open the control valve 11 at the lower end of the production tubing 2, and start the process located in the production tubing The lifting system extracts the formation fluid, starts depressurization production, controls the flow pressure at the bottom of the hole, carries out natural gas hydrate depressurization method or fluid extraction method under the condition of lower production pressure difference, and slowly increases the production pressure difference according to the actual situation; steps (4) During the process, the gas-liquid-solid three-phase produced from the hydrate reservoir 8 flows into the wellbore and is separated by the gas separator 10. The liquid-solid two-phase flows to the wellhead through the production tubing 2, and the gas passes through the wellbore annulus 13 output; during the implementation of step (4), observe the working status of the artificial lift system at the bottom of the well and the sand production at the wellhead, and monitor the sand concentration parameters at the wellhead and the change of the flow pressure at the bottom of the well in real time. Sand abnormality, if there is a sudden increase in the sand concentration or a sudden increase in the bottom hole flow pressure difference, stop the further pressure reduction production immediately, and turn to step (3), through the reciprocating cycle, the injected sand and gravel are continuously filled to replace the formation deficit. To maintain the long-term production of marine silty gas hydrate.

In order to achieve the triple goal of increasing the productivity of silty reservoirs, preventing large-area deficits in the formation, and prolonging the effective period of wellbore sand control, in this embodiment, the position of the gravel packing tool 4 at the bottom of the well is at the top boundary of the hydrate reservoir section 8, and The wellbore is depressurized for production without gravel packing tools; in the process of step (4), it also includes the process of continuously injecting water or liquid containing hydrate inhibitors into the production tubing from the packing string to ensure The fine sand produced in the formation can be carried to the wellhead while preventing the secondary generation of hydrates. In practice, the filling pipe string 3 alone fills the formation outside the pipe with sand-mixed mortar when injecting gravel, and can replenish water to the production tubing 2 during the production stage. , used to carry sand in the wellbore.

In addition, the time node from step (4) hydrate depressurization production process to step (3) gravel injection is judged according to the abnormal sand production in the wellbore, or the sudden change in the production pressure difference at the bottom of the well without artificial pressure adjustment; (3) Intermediate gravel injection to step (4) Hydrate depressurization production time point is that the gravel injection pressure rises rapidly and cannot continue to inject, and the basis for judging abnormal wellbore sand production includes bottomhole pressure fluctuations under stable production conditions, lift pump The temperature rise of the sand mill and the increase of the sand concentration monitored by the wellhead are judged, and the specific production process is determined according to the selection of the actual lifting system.

More importantly, the particle size of the sand and gravel used for filling in the step (3) is larger than the grade 1 to grade 2 of the design results using the Saucier method under the same formation conditions; the sand retention accuracy of the mechanical screen in the step (1) is greater than the same The precision of the mechanical screens used for open hole gravel packing in conventional oil and gas wells under formation conditions is grade 2-3, which helps to discharge mud or fine particles in the formation near the wellbore in time during the hydrate decomposition process, preventing wellbore blockage, and effectively Improve the pressure transfer efficiency of the hydrate wellbore and the decomposition efficiency of the hydrate, and the particle size of the sand particles used in the gravel injection process is consistent with the particle size of the sand particles used in the open hole filling in the completion stage.

Due to the continuous decomposition of formation hydrate and the production of some mud and fine particles during the long-term mining of hydrate, the formation will always be short to a certain extent, and the gravel filled in the early stage will have a certain creep, and the intermittent stop method is adopted. Pressure reduction/fluid extraction production and injection of sand and gravel into the formation outside the pipe will effectively fill this part of the deficit and prevent a large area of formation deficit; The sand control screen directly faces the frontal erosion of the formation fluid, which will reduce the validity period of the sand control operation. Based on this plan, replenishing the formation deficit in time will effectively extend the sand control validity period.

After multiple rounds of hydrate depressurization/fluid extraction and production-sand gravel extrusion process, the material exchange between near-well mud and fine silt and large-sized gravel is realized, so that the additional pressure drop near the wellbore is significantly reduced, and the sand and gravel The diameter design and the sand retaining precision design of the mechanical screen produce a synergistic effect, jointly promote the further decomposition of hydrates, and increase the productivity of silty hydrate reservoirs; moreover, the selection of open hole filling and sand control completion operations facilitates the later injection into the wellbore When using sand and gravel, there can be a smooth mortar flow channel to ensure that the mortar is intermittently squeezed into the formation outside the pipe smoothly; Creeping and subsidence, the void space in the formation is mainly in the upper part of the hydrate reservoir, so this design is conducive to the intermittent injection of sand and gravel in the later stage to ensure the smooth progress of the sand and gravel huffing and puffing mining process;

The packing string is also used as the grit huff and puff string in the later stage and the wellbore water supply string during the hydrate depressurization/fluid extraction process. The tee design realizes the switch between wellbore water supply and mortar injection, and simplifies the design of the wellbore string. At the same time, part of the mud and fine components produced in the wellbore during the hydrate depressurization/fluid extraction process can be successfully carried to the wellhead with the help of water replenishment pipeline to prevent sand plugging in the wellbore. At the same time, the pipeline can also be used as a hydrate inhibitor injection pipeline to ensure the safety of wellbore flow and ensure the continuous advancement of the sand and gravel huff and puff process.

Embodiment 2, this embodiment discloses a silty marine natural gas hydrate gravel huff and puff production device, referring to Figure 1 and Figure 2, including a production casing 1, a production tubing 2 and a packing string arranged in the production casing 1 3. There is also a lifting string (not shown) inside the production tubing 2. The lifting string is connected to the lifting pump. The gap formed between the outer wall of the production tubing 2 and the filling string 3 and the inner wall of the production casing 1 It is the wellbore annulus 13; the lower end of the production casing 1 is connected with a mechanical screen 6, and a gravel packing tool 4 is also arranged between the production casing 1 and the mechanical screen 6, and the production casing 1 is run into the hydrate The upper position of the reservoir 8, and the gravel-packing tool 4 is located at the top boundary of the hydrate reservoir 8, and the mechanical screen 6 is located in the hydrate reservoir section below it, the gravel-packing tool 4 can be The wellbore is used for decompression production, and a gas separator 10 and a control valve 11 are also installed at the lower end of the production tubing.

The outlet end of the packing string 3 is in communication with the gravel packing tool 4 and the production tubing 2 respectively. A one-way control valve 5 is provided at the connection between the gravel packing tool 4 and the production tubing 2, and the gravel packing tool 4 is also provided with a gravel packing The valve 12 is switched, and the packing string 3 is connected with the production tubing 2 under the gravel packing tool 4. When the gravel (sand) is injected, the packing string 3 alone fills the formation outside the production casing 2 with sand-mixed mortar. In the second stage, water can be added to the production tubing to carry sand in the wellbore.

Through the design of the above-mentioned production device, the formation fine particles and mud are allowed to be produced into the wellbore during the hydrate production process, and are carried to the wellhead through the effective wellbore water replenishment through the filling string; The shortfall caused by high-quality production can achieve the effect of "three birds with one stone" to improve the productivity of silty reservoirs, prevent large-scale deficits in formations, and prolong the effective period of wellbore sand control. It has promoted the development of hydrate commercial mining technology.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. The embodiments are applied to other fields, but any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solutions of the present invention without departing from the content of the technical solutions of the present invention.

Claims (9)

1. The recovery method 1. aleuritic texture ocean gas hydrate gravel is handled up, it is characterised in that comprise the following steps：

   （1）Drilling well carries out bore hole sieve tube completion to destination layer position to hydrate reservoir；

   （2）Simultaneously tripping in wellbore tubular column combination is installed；

   （3）Carry out the outer gravel flow pack of screen casing, observation stowing pressure change, and and stopping filling；

   （4）Original pipe string combination is not played out, adjusts valve flow, opening well and making production, and Real Time Observation formation sand production situation and shaft bottom Producing pressure differential changes；

   Step（3）And step（4）Switched in time according to timing node, alternately, the gravel of injection is constantly filled displacement ground Layer is in debt, maintains the long-acting production of ocean aleuritic texture gas hydrates.
2. 2. recovery method according to claim 1, it is characterised in that：The step（1）It is accomplished by the following way：Open Hydrate reservoir, using production casing sealing hydrate reservoir superstratum, tripping in machinery screen casing, hydrate reservoir is carried out naked Independent sieve tube completion now, beats artificial bottom of a well；Gravel pack tools installation is reserved between mechanical screen casing and its top production casing Interface.
3. 3. recovery method according to claim 1, it is characterised in that：The step（2）In, the mounting means of pipe string combination For：Tripping in gravel pack tools, production tube and filling tubing string, production tube and filling tubing string are located in production casing, and fill Tubing string to be filled out to connect with production tube and gravel pack tools respectively, gravel pack tools are located at the top circle of hydrate reservoir, and The arrival end of production tube is provided with control valve and gas separator, and the connectivity part of gravel pack tools and production tube is also set up There is one-way control valve, filling switching valve is additionally provided with gravel pack tools.
4. 4. recovery method according to claim 1, it is characterised in that：Step（3）In gravel-packing process, close gravel and fill The one-way control valve filled out on the downside of instrument, gravel pack switching valve is opened, close the control valve of production tube lower end, pass through filling pipe The passage that post and gravel pack tools are formed forms gravel pack layer, gravel injection process to gravel is injected outside mechanical screen casing Middle load fluid passes through mechanical screen casing, and by returning to platform well mouth in mineshaft annulus, mineshaft annulus is production tube and fills tubing string The annular space that the inwall of outer wall and generation sleeve pipe is formed；The mortar injection pump discharge pressure change in gravel injection process is observed, when Gravel injects pressure by P₀It is gradually increased to P₁, stop gravel injection, be transferred to next production phase, the P₀Injected for gravel Start pressure, P₁Maximum pressure is injected for gravel.
5. 5. recovery method according to claim 1, it is characterised in that：

   Step（3）To step（4）During conversion：The one-way control valve on the downside of gravel pack tools is opened, gravel is closed and fills Switching valve is filled out, opens the control valve of production tube lower end, starts lifting pump extraction of formation fluid, starts decompression production；

   Step（4）During from the gas-liquid-solid three-phase of hydrate reservoir output, after flowing into pit shaft, by point of gas separator From liquid-solid two-phase flow to well head by production tube, and gas then passes through mineshaft annulus output；

   Step（4）In implementation process, real-time monitoring well mouth containing sand concentration parameter, bottom hole flowing pressure situation of change, if containing The increase suddenly of sand concentration or the unexpected increase of flowing bottom hole pressure difference, then stop further decompression production, be transferred to step（3）.
6. 6. recovery method according to claim 5, it is characterised in that：Step（4）During, in addition to by filling tubing string not Break and the process of water or liquid containing hydrate inhibitor is injected to production tube inside.
7. 7. recovery method according to claim 1, it is characterised in that：By step（4）Hydrate decompression production process turns step Suddenly（3）The timing node of gravel injection shakes out according to pit shaft to be judged extremely；By step（3）Gravel injection is gone to step（4）Water The timing node of compound decompression production is the gravel injection rapid lifting of pressure, can not continue to inject；Wherein, pit shaft shakes out abnormal Basis for estimation includes bottom hole pressure surge under steady working condition, heating is sanded in lifting pump and well head monitoring sand concentration increase phenomenon Occur.
8. 8. recovery method according to claim 2, it is characterised in that：The step（3）Gravel particle diameter used in middle filling More than using 1 grade -2 grades of Saucier method design results under the conditions of same formation；Step（1）The sand block essence of middle mechanical screen casing Degree is more than 2 grade -3 of the mechanical screen casing precision used in used conventional oil gas well open-hole gravel pack under the conditions of same formation Level.
9. The quarrying apparatus 9. aleuritic texture ocean gas hydrate gravel is handled up, it is characterised in that including production casing, be arranged on life The production tube and filling tubing string in sleeve pipe are produced, lifting tubing string is additionally provided with production tube, lifting tubing string is connected with lifting pump, The space formed between the inwall of the outer wall and production casing of production tube and filling tubing string is mineshaft annulus；

   The production casing lower end is connected with mechanical screen casing, and gravel filling is additionally provided between production casing and mechanical screen casing Instrument, at the top position of production casing tripping in hydrate reservoir, and gravel pack tools are located at the top circle of hydrate reservoir, And mechanical screen casing is disposed below hydrate reservoir section, gas separator and control are additionally provided with the lower end of production tube in addition Valve；

   The port of export of the filling tubing string connects with gravel pack tools and production tube respectively, gravel pack tools and production oil The connectivity part of pipe is provided with one-way control valve, and filling switching valve is additionally provided with gravel pack tools, and fills tubing string in gravel The lower section of packing tool connects with production tube.